It is well known to use screw pumps in deep well applications such as pumping oil from wells. There are a number of challenges presented by the use of screw pumps with which existing well head drives are intended to deal. It is necessary to control the backspin that occurs on shutting down a well. Backspin is caused by two energy storage systems, inherent in deep well screw pump operation. The first energy storage system results from a fluid head in the well that on shutting off the pump drive effectively turns the screw pump into a motor. The second energy storage system results from torsion of the sucker rods linking the drive head to the screw pump. Current drive heads provide a mechanism for mitigating the backspin caused by these stored energy systems. However, present solutions may be less effective and require higher maintenance than desirable.
Reliability of backspin retarders has become a problem primarily due to increased fluid head and larger pumps than were prevalent a few years ago. Higher torque utilized by larger pumps means more energy is stored as wind-up of the sucker rod strength. Greater fluid head means more energy is stored above the pump in the fluid column which drains back through the pump causing the sucker rods to rotate backwards on shutdown. Energy stored by rod windup and fluid head must be absorbed by the backspin retarders without overheating the backspin brake. The combination of higher torque and fluid energy has put more demands on backspin retarders than earlier versions were capable of withstanding.